Arbitron is a media and marketing research firm serving the media, the mobile industry and advertising agencies. Its businesses include measuring network and local market radio audiences, surveying retail, media and product patterns of U.S. consumers, providing mobile audience measurement and analytics and developing application software used for analyzing audiences.

The price works out to $48 per share in cash, which Nielsen will finance.

Arbitron will help Nielsen track unmeasured areas of media consumption, including streaming audio.

“These integrated, innovative capabilities will enable broader measurement of consumer media behavior in more markets around the world," says Steve Hasker, Nielsen president of global media products and advertiser solutions.

Together the companies had revenues of $6 billion for the 12 months ended Sept. 30.

Nielsen's shares, which closed at $29.62 on Dec. 17, were trading slightly up, to $30.17, after the deal was announced. Arbitron's shares closed at $38.12 on Dec. 17 and opened at $47.16 on Dec. 18.